Field
Embodiments described herein relate to blind inserts that are typically used with sandwich panels.
Background
Sandwich panels are often used to form interior structures, such as walls for bulkheads, galleys, and lavatories, in aircraft. A sandwich panel generally includes two relatively thin outer panels on either side of a honeycomb panel or other lightweight material, such as Styrofoam. A sandwich panel may not have sufficient material strength to handle the stresses caused by a screw that is screwed into the sandwich panel (e.g., to hold a bracket or to connect two walls together). Thus, sandwich panels may employ inserts to decrease stresses caused by screws. A hole can be drilled into a sandwich panel and the insert can be affixed (e.g., with glue or epoxy) into the hole. The insert includes a threaded nut that can receive the screw and a surrounding insert material that increases the area of the panel over which forces transmitted through the screw and transferred to the panel, thereby decreasing stresses.
There are two general types of inserts: through inserts and blind inserts. A through insert extends all of the way through a sandwich panel. By contrast, a blind insert only extends partially through a sandwich panel. With a through insert, a threaded end of a screw threaded into a first side of the insert can be accessible from the second side of the insert. Thus, the threaded end of the screw can be locked to the nut of the insert (e.g., via safety wire) to prevent the screw from loosening due to vibrations. With a blind insert, the threaded end of the screw threaded into a first side of the insert is not accessible from the second side.
To prevent loosening of a screw in a blind insert, the nut of the threaded insert is often crimped after the insert is formed. Passages are formed in the surrounding insert material that enables a crimping tool to reach the nut. The crimping of the nut results in a threaded aperture that is no longer circular. The out-of-round threaded aperture caused increased friction with the screw when the screw is inserted, thereby improving retention of the screw after installation (e.g., in vibrating environments). However, the crimping process adds several steps to the process of manufacturing a blind insert. Furthermore, typical processes have resulted in poor product yield because small variations in crimping can result in a large difference in the amount of friction between the out-of-round threaded aperture of the nut of the insert and the screw. Thus, a high number of produced parts are scrapped because the crimping operation results in too much or too little friction between the threaded aperture of the nut and the screw.